JPH0470802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission power control device for a transmitter used in a satellite communication earth station.

[Conventional technology]

Conventionally, transmitting equipment consisting of transmitting frequency converters and power amplifiers used in satellite communication earth stations suffers gain fluctuations due to fluctuations in ambient temperature, so temperature compensation is used to prevent this and prevent fluctuations in transmission power. . In addition, in order to downsize satellite earth stations, the transmitter is downsized and installed at the back of the antenna or at the focal point. In this case, the transmitter is divided into an indoor part and an outdoor part, and a cable is connected between them. A configuration in which connections are made with

[Problem that the invention seeks to solve]

In such a transmitting device, it is necessary to stabilize the gain because variation in gain due to outdoor temperature causes variation in transmission power. Conventionally, when temperature compensation of gain is performed for this purpose, it is difficult to achieve accurate compensation, and loss fluctuations due to temperature of the cable connecting indoor and outdoor parts, and gain fluctuations of outdoor equipment and indoor equipment separately occur. The problem is that there is no compensation for this.

An ALC circuit is also used to keep the output level constant, but in this case the output remains constant even if the transmitter input level is changed, making it impossible to change the transmission power.

Furthermore, in this ALC circuit, the gain is controlled to the maximum when there is no input signal, so in order to perform appropriate level compensation for burst-like inputs such as packet transmission, the ALC response must be extremely fast. However, there is a problem in that the desired output cannot be obtained because there is actually a limit to this response speed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission power control device that can appropriately compensate for gain fluctuations and can also appropriately compensate for packet transmission.

[Means for solving problems]

The transmission power control device of the present invention configures an ALC loop that detects the level of an input signal and the level of an output signal of a transmitter and controls its gain, and includes a comparator and a comparator that compares the input level with a reference value.
A hold circuit is provided to keep the operation of the ALC loop in a fixed state, and when the input level of the comparator falls below a reference value, the hold circuit is driven and the gain of the ALC loop is fixed at the previous value. However, the gain is compensated to a constant value greater than a predetermined value.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

The figure shows a system diagram of an embodiment of the present invention. In the figure, the transmitter is an indoor device IDU and an outdoor device ODU
The two are connected by cable CBL.

The indoor device IDU includes a first frequency converter U/
C-1, an input level detector DET1 for a signal input to the input terminal 1 of the indoor device IDU, and a comparator COMP for determining the presence or absence of a level based on the output of this input level detector DET1.

The outdoor device ODU also includes a second frequency converter U/C-2, a voltage controlled attenuator ATT for changing the gain, a power amplifier PA, and a directional coupling for branching a part of the output. equipment DC, outdoor equipment
It consists of an output level detector DET2 for the signal output from the output terminal of the ODU, an error amplifier A for ALC operation, and a hold circuit HLD.

According to this configuration, the IF input signal of the indoor device IDU is converted to a transmission frequency by the first frequency converter U/C-1 and the second frequency converter U/C-2, and is amplified by the power amplifier PA. and becomes the transmitted output.

At this time, the input level detector DET1 detects the input level, and the output level detector DET2 detects the output level from a part of the output signal branched by the directional coupler DC. The signal is amplified by the error amplifier A, and the output power is controlled by controlling the voltage controlled attenuator ATT based on the amplified signal. That is, by forming a negative feedback loop in which the output of the output level detector DET2 matches the detected value of the input level detector DET1 as a reference, the ALC circuit operates and its gain is controlled to a constant value. are doing.

However, at this time, the hold circuit HLD connected to the error amplifier A causes the input level detector DET1 to
When the input level falls below a predetermined value, this is detected by the comparator COMP, and this output drives the hold circuit HLD to hold the previous input level, thereby performing voltage control attenuation. In the device ATT, this voltage is held and the gain is fixed and held above a certain level.

Therefore, it is possible to effectively compensate not only for gain fluctuations due to temperature of the outdoor device and indoor device, but also for loss fluctuations due to temperature of the cable connecting the indoor portion and the outdoor portion. Furthermore, since the gain is held constant at this time, it is possible to transmit fluctuations in the input level as they are to the output, thereby changing the output.

Furthermore, the gain is held fixed by the hold circuit, which prevents the gain from reaching its maximum when there is no input signal, unlike conventional ALC circuits, so it is possible to transmit packet signals whose amplitude changes in a burst pattern without any problems. I can do it. In this case, since high speed ALC operation is not particularly required, the configuration of the device is also easy.

〔Effect of the invention〕

As explained above, the present invention comprises an ALC loop that detects the level of an input signal and the level of an output signal of a transmitter and controls its gain, and includes a comparator and a comparator that compares the input level with a reference value.
A hold circuit is provided to keep the ALC loop operation in a fixed state, and when the input level of the comparator falls below the reference value, the hold circuit is driven to fix the ALC loop gain at the previous value. This structure compensates for gain fluctuations due to the temperature of the transmitter and keeps it constant, allowing output to be sent out according to the input level, and preventing maximum gain when there is no input signal, making it possible to suppress gain fluctuations due to the temperature of the transmitter, such as packet signals. This also has the effect of allowing communication to be carried out without any problems.

[Brief explanation of the drawing]

The figure is a system diagram of an embodiment of the transmitting device of the present invention. IDU...Indoor equipment, ODU...Outdoor equipment, CBL
...Cable, U/C-1...First frequency converter, DET1...Input level detector, COMP...
Comparator, U/C-2... second frequency converter,
ATT...voltage controlled attenuator, PA...power amplifier,
DC...Directional coupler, DET2...Output level detector, A...Error amplifier, HLD...Hold circuit.

Claims (1)

[Claims] 1. In a transmitting device that amplifies or frequency converts an input signal and transmits it, an input level detector detects the level of the input signal, an output level detector detects the level of the transmitted output signal, and a detection value of each level detector. An ALC loop is configured with means for controlling the gain of the transmitter based on the reference value, and a comparator for comparing the input level with a reference value, and a hold circuit for keeping the operation of the ALC loop in a fixed state. 1. A transmission power control device, characterized in that when an input level in a device becomes below a reference value, the hold circuit is driven to fix the gain of the ALC loop at the value immediately before that.